Because meals had become a situation of social and spiritual exclusion and divisiveness they become an arena in which Jesus brings the kingdom of God and obliterates those barriers, much to the annoyance of those who maintain the barriers.
From Contagious Holiness:
… we discover Jesus challenging the purity laws of his day, or at least the way in which they are applied to exclude various categories of Israelites. Scandalously, he associates with the notoriously wicked, but he is willing to feast with the scrupulous religious leaders as well. Jesus’ table fellowship with sinners reflects his willingness to associate with them at an intimate level, but not merely for the sake of defying convention or enjoying a party. In each case various textual clues, if not explicit statements, demonstrate that Christ is indeed calling them to repentance and summoning them to be followers. At the same time, his is ready to accept them at the slightest sign of a positive response and does not follow the Essene pattern of requiring a lengthy period of probation to prove themselves. In various ways, Jesus’ meals, and especially his wilderness feedings, evoke the theme of the Messianic banquet but again suggest a far more inclusive guest list than most Jews anticipated. Little wonder that when his behaviour is caricatured he is described as a ‘glutton and a drunkard’.
Craig L. Blomberg, Contagious Holiness, IVP, 2005, pg. 167.